4 ms·
Always, always, always generate your own SSH moduli.
by disposablezero 10y ago
Always, always, always generate your own SSH moduli.
- notyourwork 10y agoFor those uninformed you should expand on this to. It is a great suggestion but a statement like this to a uninformed isn't very helpful.
- poisonarena 10y agoplease elaborate!
- knweiss 10y agoFrom the OpenSSH moduli(5) man page: "When performing Diffie-Hellman Group Exchange, sshd(8) first estimates the size of the modulus required to produce enough Diffie-Hellman output to sufficiently key the selected symmetric cipher. sshd(8) then randomly selects a modulus from /etc/ssh/moduli that best meets the size requirement." The problem is a) OS distributions ship pre-computed moduli in the /etc/ssh/moduli file. I.e. most users don't change these moduli. This facilitates pre-computation attacks. b) These moduli are often too short (<2048 bit). You can create your own moduli with ssh-keygen (see the "MODULI GENERATION" section in the ssh-keygen manpage). FWIW: Here's my open bug for RHEL7 where I try to convince Red Hat to improve the situation (including more details and references): https://bugzilla.redhat.com/show_bug.cgi?id=1396943 https://bugzilla.redhat.com/show_bug.cgi?id=1396943
- alkonaut 10y agoMost people with desktops are using Windows. What are the best practices there?